Semiconductor integrated circuit devices need to operate at high speeds. High-speed operation is mainly driven by miniaturization of semiconductor devices such as transistors, reduction in wiring resistance, reduction in dielectric constant of interlayer insulating films, or the like. However, high-speed operation in these technological areas is reaching the limit.
Therefore, in order to promote higher speed operation, germanium (hereinafter, also referred to as Ge) as a semiconductor material having higher carrier mobility has attracted attention, instead of silicon (hereinafter, also referred to as Si) which is conventionally used as a semiconductor material.
Applications for filling Ge as a Ge film in a recess such as a trench or a hole formed on an insulating film such as a silicon oxide film (hereinafter, also referred to as an SiO2 film) or a silicon nitride film (hereinafter, also referred to as an SiN film) by a chemical vapor deposition method (CVD method) are being studied.
However, when the Ge film is filled in a deep hole or trench by the CVD method, the step coverage may deteriorate generating voids. When a void occurs, since the resistance value increases, a method of filling a recess in which as little of a void as possible is generated is needed.
For example, although not a Ge film, a technique of forming a silicon film in a recess such as a hole or a trench, etching it in a V-shaped section, and then filling the silicon film again has been proposed. Thus, void-free filling may be achieved.
Moreover, although a halogen gas or a high-temperature thermal oxidation treatment is used for etching of a Ge film, the selectivity to an insulating film or the like is not sufficient, and when a Ge film is being etched, even other films may be etched. Thus, it is difficult to apply the proposed method to the Ge film. For this reason, a method of filling a Ge film in a recess in a void-free manner has not been accomplished.